In many cases it is desirable to track, receive notifications and/or apply various rules as a person (or other entity) moves about, as time passes, or as different people (or entities) enter or leave the proximity of the tracked person or entity. Consider the case of a convict in a work release program. It is desirable for a parole officer to monitor the convict, to ensure, for example, that he is physically at work when he should be, that he is not violating any restraining order, etc. But such monitoring can be labor-intensive and costly. Also, consider a parent desiring to monitor the location of a mentally handicapped child prone to wander off. In other examples, a Department of Homeland Security agent may wish to know when a large quantity of ammonium nitrate is approaching particular locations. A parent may want to know when a sexual predator is within a certain distance of their children. A chemist may want a laboratory to report when lithium and water are within some distance of one another. And a self-reporting nano-material may report whenever another nano-material is detected within some sensitive zone. These and many other scenarios for monitoring physical and/or virtual entities based on a set of rules and in relation to various zones tend to be difficult and expensive manual efforts at best.